Mystery rocks is a bouldering area in Penannt hills. Some of the problems are quite high ball with scary top outs. There is plenty of room for more routes just bring a brush as the rock need a good clean on new problems. For a guide check out the Crag X Mystery Guide
To get there drive to the end of Behan Place off Boundary Rd in Cherrybrook. Take the track that heads off on the right of the barrier and head right when you hit the main track. After about 200m after you climb a few steps the walls of area C will appear.